Now here is an interesting and rew
arding genus of somewhat unknown tender shrubs for the greenhouse. Whether you want an attractive foliage plant, gloriously scented flowers or to grow an unusual but useful fruit Carissa grandiflora or Natal plum (once known as Acokanthera) ticks all the boxes.
Perhaps the only drawback is the spines, not thorns as such but it’s still a tad prickly- though in their native South Africa even this feature is employed as Carissa makes an excellent hedging plant. Not hardy this is tender but also tough and as long as kept just frost free will endure quite easily and even if damaged can be pruned quite severely and will come back strongly. You may come across this whilst on holiday in southern Spain, the Canaries and in other warmer spots in the Mediterranean where it is grown for ornament and for the scented flowers. There it may reach ten feet high and half as much across but here in a pot or tub it remains relatively more compact.
The small slightly glossy oval leathery leaves much resemble box or a ruscus but the thorns or rather spines behind them are the giveaway. The flowers are large, star shaped, white and in many ways resemble citrus- indeed the plant could, errantly, be thought to be a near relative, and requires very similar treatment. However these flowers are followed by red fruits the size of a large plum, conical at either end with a tough skin. These are not usually esteemed raw for dessert but once cooked with sugar make a very pleasing dish and as they are rich in vitamins and anthocyanins they can also make a very healthy addition to our diet. The plants are not widely found commercially in the UK but the seed is available from some seed companies, comes up readily and the young plants can be grown on to crop in only a few years. However most will grow this more for the attractive foliage and lovely flowers. Tough plants they are not particular to compost thriving in any reasonable mix though preferring a rich well drained one.
They are also conveniently immune to erratic watering regimes, indeed they survive neglect better than almost all other greenhouse subjects. Although occasionally bothered by mealy bug few other pests or diseases are ever a problem though sometimes the leaves and ends of shoots may die back during winter but this is rectified with a trim back in spring when growth resumes. There are several species and some slight confusion with re-naming by nomenclatural botanists but all are remarkably similar and equally good value. Carissa grandiflora / macrocarpa is the original Natal plum, ‘nana’ is a lower growing version with more tubular flowers and rounded lobes. C. acocanthera has larger leaves, up to four inches long, and similar white flowers with the same gorgeous scent